Street fighting broke out in Ukraine’s second-largest city and Russian troops squeezed strategic ports in the country’s south Sunday, advances that appeared to mark a new phase of Russia’s invasion following a wave of attacks on airfields and fuel facilities elsewhere in the country.Street fighting broke out in Ukraine’s second-largest city and Russian troops squeezed strategic ports in the country’s south Sunday, advances that appeared to mark a new phase of Russia’s invasion following a wave of attacks on airfields and fuel facilities elsewhere in the country.